The present invention relates to a centering and gripping tool for at least one part to be fixed in position.
Centering and/or gripping tools are generally mounted securely on carrier frames. Such a centering and gripping tool can be for example of the type described in French patent 2 757 437 and comprises a guide member carried at the end of a casing or body and gripping members as well as pivotal and translatory guide means for the gripping members between a centering position in which the gripping members are retracted inwardly of the guide member and a plurality of gripping positions in which the gripping members project outwardly of the guide member, said guide means being arranged to product simultaneously the pivotal and translatory drive of said gripping members.
So as to promote good gripping behavior, there is generally provided a reference surface or bearing surface on the casing, for example with the help of a corresponding member surrounding the guide member, and against which the part to be secured rests, facing the gripping means in the deployed position.
This type of centering and gripping tool is thus used to secure parts of the same type, which is to say that they generally have a through passage of the same diameter and whose constant thickness corresponds to the given interval between the bearing surface and the part and the gripping means in the gripping position.
A problem thus arises when it is desired to use this centering and gripping tool for a part having a through passage of the same diameter but which has a different thickness. It is then necessary to exchange the tool for another corresponding to the new thickness, which is to say whose given interval between the bearing surface and the part and the gripping means is suitable for this new part.
Another possibility consists in modifying the part forming the bearing surface and which is fixed on the casing to define this new interval.
In both cases, this gives rise to a loss of time to the extent to which it is necessary to dismount the centering and gripping tool and then to mount a new tool or to modify this tool.
So as to overcome this drawback, the present invention has for its object to provide a centering and gripping tool which permits easily dismounting the centering and gripping tool and to effect in a simple manner the gripping of the pieces having the same diameter for centering but which can be of different thicknesses.
To this end, the invention has for its object a centering and gripping tool for a part to be secured, comprising a through passage and adapted for said tool, said tool comprising a guide member, at least one gripping means mounted on the guide member, and a body enclosing the drive and guide means for said tool said gripping means being movable, under the action of drive means, between a centering position in which it is retracted within the guide member and a gripping position in which it projects outside the guide member such that the part to be secured is gripped between the gripping means and a support surface, said tool also comprising a securement support comprising a support part provided with a passage in which is mounted the guide member of said tool, said guide member projecting beyond the free end of said guide part, said free end constituting the reference surface or support surface of the part to be secured whilst the body of the tool is gripped against a support surface opposite said support part, characterized in that a removable interchangeable shim is interposed between the body of the tool and the support surface opposite the support part against which the body is secured.
Thus in a preferred manner, the securement support serves for mounting the tool according to the invention on a receiving surface and facilitates changing the tool to the extent to which, the support remaining fixed, only the active portion of the centering and gripping tool is replaced (gripping meansxe2x80x94guide memberxe2x80x94body) by another on the support.
Thus, the free end of the support part constitutes the reference surface or bearing surface of the part to be secured and the interval between this bearing surface and the gripping means in the gripping position, corresponding to the thickness of the part to be secured, is predetermined by the portion of the guide member projecting from the passage of said support part. As a result, the interposition or not of a shim between the body and the support surface opposite to the support part permits modifying this interval because it influences the projection of the guide member at the free end of the support part.
Because of this, the thickness of the shim interposed between the body of the centering and gripping tool and the support surface against which is gripped said body, contributes to define the size of the interval.
Thus, the securement support of the centering and gripping tool according to the invention facilitates not only changing the tool but also permits defining for a same tool a support surface for the part to be secured, whose distance relative to the gripping means in the gripping position can vary because of the positioning of this tool in the support.
As a result, when the part to be gripped changes and has a different thickness, the interval between the gripping means in the gripping position and the support surface can be modified, this modification of the interval being thus able to be carried out in a simple manner by positioning a shim of a suitable thickness or by changing a shim already installed and replacing it with a shim of another suitable thickness.
Thus, the centering and gripping tool according to the invention is usable for parts provided with a through passage of the same diameter but having different thicknesses, by simple emplacement or changing of the interchangeable removable shim.
According to a first modification of this embodiment, the shim is rigid and its thickness corresponds to a predetermined size interval.
According to a second modification of this embodiment of the invention, the shim is resiliently deformable and can be made for example of an elastically deformable material or else have a structure with a resilient deformation property such as a Belleville washer such that, during variations of the thickness of the parts to be gripped, the resilient deformability of the shim permits compensation of these variations by permitting an axial displacement of the centering and gripping tool relative to the securement support to permit good positioning of the gripping means and hence a perfect holding of the part. Thus, the thickness of the shim defines the interval between the support surface and the gripping means but moreover, its deformability permits an adaptation of this interval resulting from differences in the thickness of parts, for example that are supposed to be of the same thickness.